The continuous prodn. of basic zinc carbonate (I) is carried out by continuously contacting a Zn salt soln. with an NaOH-contg. Na2CO3 soln. while maintaining a pH of 7-10, the residence time of the mixt. in the reaction vessel being 10-1800 (pref. 45-300) sec. (I) is used as an activator and filler for rubber and for the prepn. of active Zn oxide (also used as a rubber activator and filler). The process gives high space-time yields of a high-purity product with good filterability; the filtrate has a very low Zn content, thus minimising waste-water treatment problems. The product can be converted (by calcination) into high-purity ZnO with a bulk density of 25-30 g/100 ml. The equiv. ratio of NaOH to Na2CO3 is pref. 25:75 to 80:20, esp. 50:50 to 60:40. The Zn salt is pref. Zn (NO3)2, ZnCl2 and/or ZnSo4, opt. in admixture with alkali(ne earth) metal salts. The initial solns. are pref. preheated to 50 degrees C before contact. The product is pref. converted into ZnO by calcination at =600 degrees C.
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